Gas piston for firearms



Jan. 22, 1952 E, M H V GAS PISTON FOR FIREARMS Filed May 6, 1948 m 0 E Mm: W A2 a I Patented Jan. 22, 1952 2,582,989

UNl'iE stares PATENT OFFICE GAS rrs'roN Fon FIREARMS T Earle M. Harvey, Springfield, Mass.

Application May 6, 1948, Serial No. 25,442

zfoleims. (o1. s9-191) (Granted under the act of March 8, 1883, as 1 amended April 30, 1928; 370 0. G. 757? The invention described herein may be manuas other objects and advantages thereof will factured and used by or for the Government for clearly appear from a description of a preferred governmental purposes without the payment of embodiment as shown in the accompanying any royalty thereon. drawings in which:

This invention relates to an improved gas Fig. 1 is a longitudinal sectional view of a. system for a firearm, particularly a gas system gas cylinder and piston in accordance with this adapted to furnishing operating force for an invention shown in assembled relationship with automatic firearm. respect to a firearm barrel.

In gas operated firearms of modern design, Fig. 2 is a view similar to Fig. 1 but showing there has been in increasing tendency to locate it) t e p to in the rearward position. the take-oil point for the operating gases in a Fig. 3 shows a modified arrangement of the region of the barrel very close to the chamber gas piston construction "shown in Figs. 1 and 2. end thereof. Such location of the gas take-off Fig. 4 is an exploded perspective view of the has the obvious advantage of decreasing the gas piston showing one means of securing the length of the operating member connecting bestem to the piston.

tween the gas system and the breech mechanism Referring to the drawingsa bracket portion l I and hence afiecting an appreciable weight reof a gas cylinder I 0 surrounds a barrel I of an au ti n. automatic firearm in the vicinity of a gas port 2 Such location, however, necessarily results in provided in such barrel. Althou ot i ted gases being furnished to the gas system at an thereto the sport 2 m y be located close to extremely high pressure. Accordingly a high the chamber end of the. barrel l without sacri-. intensity impact blow is received by the breech ficing any safety or reliability of operation inasmechanism where a piston member. of convenmuch as the gas system embodying this invention tional design is utilized. Furthermore, the 1111- is particuluarly fiectiv in op ratin with hi h tial force on convenional piston members is so 26 pressure gas.

great that the breech action is generally opened The gas cylinder U is Secured t0 t e barrel in a very short time after exposure of the gas I by any suitable means, such as by a transverse port to the gases by passage of the bullet along pin I2. A gas passage [3 is provided through the bore. Accordingly the breech mechanism gas cylinder 10 Communicating between gas p may sometimes open while there is still an excesso 2 and the interior of a rearwardly p g Cy sive amount of gas pressure existent in the drical recess 14 provided in gas cylinder in. A

chamber. forwardly opening cylinder hole I5 is also pro- It is an object of this invention to provide vid d in as cyli r l0 un at w rean improved gas system for automatic firecess l4 and coaxial therewith. The rear portion arms which, although not limited thereto, is parof recess I 4 is provided with interior threads [4a ticularly efiective for operation by gases received in o which a hollow nut It is screwed. from the high pressure regions of the barrel. A piston 20 is provided having a maximum di- It is a particular object of this invention to m ter yl dri l p r d a r ly provide an improved gas cylinder and piston arextending reduced diameter shank portion 22.

rangement for automatic firearms wherein the ,0 Portion 2| of piston 20 cooperates with the walls effective area upon which the gases impinge on of recess II in gas cylinder Iii in bearing relathe piston may be selected within wide limits in tionship, while the shank portion 22 of the piswhich the maximum diameter of the piston ton 28 cooperates with the interior surfaces of remains unaltered with a given size gas port,to hollow nut IS in bearing relation hip. The ear-. control the acceleration of the piston, and hence ward stroke of piston 20 is limited by engageof the breech operating member. ment of the maximum diameter portion 2| with It is also an object of this invention to provide the nut Hi. Just prior to the end of the maxian improved gas cylinder and piston arrangemum stroke of the piston, an exhaust port 35 is ment for automatic firearms wherein an exhaust provided in bracket 1 l which communicates be.-

port is opened at the end of the stroke of the m tween recess l4 and the outside of such bracket piston thereby readily permitting the exit of thereby permitting the gases admitted to such the combustion products, hence substantially recess to escape to the atmosphere but not until diminishing the formation of deposits of carbon substantially the end of the power stroke of the and other deleterious substances. piston. V

The specific nature of the invention as well The rear end of piston 20 is connected in any 3 suitable manner, for example, by abutment therewith, to a movable breech operating member 30. It should be understood that the construction of the breech mechanism constitutes no part of this invention and the breech operating member comprises any conventional form of mechanism for accomplishing the unlocking and opening of the breech. The total stroke of piston 20, and hence the distance under which it can impart rearward force to breech operating member 36 is preferably substantially less than the entire stroke of breech operating member 30.

The piston is also provided with-a forwardly projecting portion 24 which is shaped to cooperate in bearing relation with hole l5 in gas cylinder Iii; A plurality of spaced annular grooves 25 are provided in this forwardly projecting portion 24 to produce an improved seal between that portion of the piston and the wall of hole 15. If desired, corresponding annular grooves 36 may be provided in the wall of hole 85' which increases the sealing effect between portion 24 and hole I5.

A forwardly facing shoulder 23 is thus provided on the piston 20 by the juncture of maximum diameter portion 2 I and forwardly projecting portion 24. This shoulder 25 limits the forward movement of piston 23 by abutting against the base of the recess I4. The length of forwardly projecting portion 24 is somewhat greater than thetotal stroke of piston 20 so that such portion will re main in bearing relationship with ho e id to provide at least a two-point bearing of the piston, at all times.

In operation, the gases developed in the firing of a cartridge flow through gas port 2 and cylin der passage I3 into recess I4 ofgas cylinder it, impinging against shoulder 26 of piston 2t. linitially however, the gases impinge on only a small area of the shoulder 26 and such. small area is defined by the size of gas passage I3. Thus the gases impinging on such a smallsurface produce but a slight acceleration of the piston initially. As the piston moves away from the end .wall of the recess I4 however, the gases act against the full annular area of shoulder 26 withfull energy.

The area of the annulus on which the gases operate being substantially smaller than the total area or" the major piston diameter, it becomes possible to allow the piston a greater travel length in achieving a given terminal velocity than would be the case if the. gases operated on the entire major diameter 2|. This greater length of travel for a given terminal velocity increases the piston travel time and delays the'opening of the breech; The time delay so achieved permits placing the gas cylinder nearer the combustion -chamber of the firearm than otherwise would'be permissible.

This construction permits the use of a'piston having dimensions of such magnitude that the piston strength between the shank portion 22 and the shoulder 26 of the major diameter 2I will be great enough to permit the use of a heavy oper' ating slide with the high impact sustained by the piston as the latter is driven to its battery position to limit the forward travel of the slide.

The gases in exhausting, therefore sweep over the entire area of the cylinder which is at any time exposed to the full pressure of the gases, and over the exterior of the piston stem, removing all carbon deposits and deleterious substances from these surfaces and carrying them out of the cylinder.

In adapting this. actuating mechanism. to a series of different guns, or to similar guns firing different charges the major diameter of the piston and the diameter of the gas port remain constant. The effective piston area is adjusted to the requirements of a particular weapon by varying the diameter of the piston portion 24 and stem hole I5. Thus a number of weapons difiering widely in ballistic characteristics may be actuated by a gas cylinder assembly of which all basic physical dimensions excepting two may be identical in all cases.

It will be further noted that as the piston is at all times guided by a two line contact, this construction permits a very substantial clearance to exist between piston body 22 and the hole in nut I 6, with the advantage that any reasonable eccentricity of the nut with respect to the recess I4 and cylindrical hole I5, occurring in manufacture, does not affect the alignment of the piston with the gas cylinder, and hence does not adversely affoot the functioning of the mechanism.

A modification of the structure shown in Figs. 1

and 2 is illustrated in Figs. 3 and 4 wherein the piston stem and stem hole can be more readily varied without the necessity of permanently a1-.- tering the bracket I I or the piston. In such figures the same bracket I I is utilized and surrounds barrel I as before-mentioned. Bracket It is however, provided with a forwardly opening recess 31. A rearwardly opening cylindrical hole 38 is pro vided in bracket I I communicating with recess 37 and coaxial therewith.

- A piston 39 having a head portion 40 and a shank M is placed in recess 3? with head 49in bearing, relationship therewith. Shank 4! pro,- jects through hole 38. A transverse hole 42 is provided in head 40 and a slot 43 in the forward race of such head communicates with hole 42 as shown in Figs. 3 and 4. A piston stem 45 is removably attached to piston 39 by means of a ball 44 connected to the end of such stem by a neck portion 49,v ball 44 being slidably engageable with hole 42. Neck portion 49 cooperates with slot 43 to permit ball 44 to engage hole 42.

Stem 45 is supported by a hollow nut 4G in the forward portion of recess3'l. Such nut is secured Within. recess 31' by threads 47. A reduced diameter portion 48 is formed on the rear end of nut 46 to reduce the initial force of the gases impinging on the face of piston head it when such head is in contact with portion 43. Thus the gases can initially act only on the small area of the piston face left exposed in the battery position of the piston.

- From this construction it is readily apparent that the efiective piston area against which the gases can operate may be easily varied by changing piston stem 45 to one of a larger or smaller diameter by simply removing nut 46,. removing stem 45 and piston 39 forwardly out of recess 31 and sliding such stem out of hole 52. Nut 48 must be replaced with a nut having a hole corresponding to the diameter of the stem selected. The swiveling action afforded by the ball and socket construction permits self-aligning of the stem in nut 46. It is obvious that other selfaligning connections may be utilized if desired as long as convenient disassembly is provided. It should be added that the operation of the piston arrangement illustrated in Figs. 3 and i is identical to that previously described.

I claim:

1. In a firearm having a barrel, a gas cylinder secured thereto, and gas passage means communicating the interior of the gas cylinder with the barrel, a breech actuating mechanism comprising in combination, a reciprocable breech operatingmember disposed rearwardly of the gas cylinder; a cylindrical piston having an enlarged head portion slidably disposed Within the gas cylinder and responsive to the flow of gases from the barrel, said piston having an integral shank portion' projectin'g rearwardly through the gas cylinder" in bearing relationship and arranged to impartgf imomentum to said breech operating memberas said piston head portion is driven rearwardly, a plug threadably secured in the front end of the gas cylinder, said plug having a hole centrally therethrough and being selected from-a group wherein the hole of each plug is of a different diameter, a cylindrical stem member slidably disposed in said hole in said plug and of such diameter as to be in bearing relationship therewith, and interconnecting means on the rear end of said stem member and in said piston head for replaceably securing said stem member in abutment with the front face of said piston'head whereby the area thereof responsive of said stem member and a ball portion of greater diameter than said neck portion fixedly secured to the rear end thereof, said piston head portion having a transverse hole therethrough for slidably and rotatably receiving said ball portion and a slot parallel to said hole and in communication therewith for passage of said neck portion, said neck portion being of smaller diameter than the width of said slot whereby said stem portion is swivelly connected to said piston in order to permit self-aligning movement of the former with respect to the latter for preventing binding of said sliding stem member in said hole in said plug.

EARLE M. HARVEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,136,695 Miclaus Apr. 20, 1915 1,366,863 Berthier Jan. 25, 1921 1,534,486 Bang Apr. 21, 1925 1,738,501 Moore Dec.3, 1929 2,058,897 Marek Oct. 27, 1936 2,346,954 Williams Apr. 18, 1944 2,372,339 Roemer Mar. 27, 1945 FOREIGN PATENTS Number v Country Date 504,934 France Apr. 26, 1920 273,300 Great Britain Sept. 21, 1928 393,195 Great Britain June 1, 1933 195,364 Switzerland Apr. 16, 1938 501,884 Great Britain Mar. 7, 1939 

